摘要:

Motivated by observational and experimental data on large-scale vortices close to the geostrophic balance we perform an asymptotic analysis of the barotropic and baroclinic rotating shallow-water systems in order to describe slowly-evolving monopolar coherent structures. The spherical and the paraboloidal geometries which are, respectively, relevant for planets and experiments with fast rotation are both studied. We analyse in detail the problem of long-living localised vortices of axisymmetric shape and find the anticyclonic solutions of a prescribed form on the sphere. In the paraboloidal geometry an arbitrary strongly non-linear axisymmetric structure may drift preserving its form for long enough times. We extend this study to the baroclinic two-layer model and find similar results with an important distinction that solitary vortices may be cyclones as well, their sign depending on the physical parameters of the model. The applications of this results in astrophysical, oceanographic and laboratory context are discussed.

ISSN:0309-1929    

DOI:10.1080/03091929608208965

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Two and three-dimensional oceanic flows around small islands patterned after Barbados, W.I. (13° 10′ N latitude: 59° 30′ W longitude) were modeled numerically to investigate island wake effects. The two-dimensional simulations closely agreed with laboratory flows, for both attached and shedding wake regimes. As expected, results for a flat bottom confirmed that the Coriolis terms strongly affect pressure but not the flow.

ISSN:0309-1929    

DOI:10.1080/03091929608208966

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We discuss the hydrodynamic stability properties of a one-dimensional quasi-steady marine current, driven by a density excess caused by low temperature or high salinity, and flowing over a regular slope, taking bottom-erosion phenomena into consideration. The term density-turbidity current is used here for a thermohaline density current, with that density increased by entrained sediment. Thermohaline currents are of fundamental importance with regard to the Earth's climate, and the same must apply to density-turbidity currents.

ISSN:0309-1929    

DOI:10.1080/03091929608208967

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this paper we discuss the application of a finite-volume multigrid method to solve three-dimensional thermally driven convection in a highly viscous, incompressible fluid with a variable viscosity. The conservation laws are solved in the primitive variable formulation, A second-order control volume method is used as discretization. Two schemes are used for time stepping, a second-order implicit-explicit scheme based on the Crank-Nicolson and Adams-Bashforth method, and a fully-implicit -method. The implicit system of nonlinear equations are solved using multigrid iteration with the SIMPLER method as smoother. In this paper, we describe the implemented multigrid method and investigate its efficiency and the robustness for different viscosity contrasts. Convergence tests showed that with a small modification of the SIMPLER method, the multigrid method exhibits a satisfactory convergence rate even for viscosity contrasts up to 109. Three cases of time-dependent thermally driven convection with viscosity contrasts up to 105are considered and discussed and the multigrid method has demonstrated its robustness also for these cases. Further, we have also compared the computational efficiency of the two time stepping methods. It appeared that the fully-implicit scheme is a little more efficient than the implicit-explicit scheme for a constant viscosity and it was considerably more efficient for a viscosity contrast of 103

ISSN:0309-1929    

DOI:10.1080/03091929608208968

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Numerical simulations are described that strongly suggest that any large buoyant mass in the Earth's outer core will be rapidly broken up into plate-like structures elongated in the directions of the rotation axis and of the prevailing magnetic field, giving rise to the highly anisotropic motions foreseen by Braginsky and Meytlis (1990) which will then form the dominant characteristic of the local fluid flow. This result casts serious doubt on the hypothesis of Moffatt (1989) that core flow is driven by buoyant parcels or plumes periodically released from Earth's inner core.

ISSN:0309-1929    

DOI:10.1080/03091929608208969

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We study MHD time evolution of initially rigidly rotating radiative zone of a G-type star subject to the effect of the magnetic field and of the deceleration of the surface angular velocity. We solve MHD equations of an unsteady axisymmetric Eddington-Vogt-Sweet (EVS)-type flow in the radiative zone, especially with respect to the angular velocity and the toroidal magnetic field, by using the Spectral method of solution. Three kinds of poloidal magnetic configurations (see Figure 1) are examined.

ISSN:0309-1929    

DOI:10.1080/03091929608208970

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor